AQNMOL logo
Advanced Quantum-Nano Materials & Optoelectronics Laboratory
 
 

QR code_Prof. Jihoon Lee

Kwangwoon Univ. KOR ver website

Kwangwoon Univ. Eng ver website

Kwangwoon College of Electronics and Informattion Engineering

Dept. of Electronics and Communications Engineering

 

University of Arkansas


Sam M. Walton College of Business

 

ERC 선도연구센터

BK 21 PLUS

Engineering Research Center, Holo-Digilog Human Media

Ministry of Science, ICT and Future Planning

Ministry Of Education

NIPA

KCC

Ministry of Education, Science and Technology

ITRC logo

ITRC Forum 2011

 

 

- Journal Editor -

3D Research

NRL cover

 

 

- Research Highlight -

 

Journal Cover: Precise Control of Configuration, Size and Density of Self-assembled Au Nanostructures on 4H-SiC (0001) by Systematic Variation of Deposition Amount, Annealing Temperature and Duration

(Journal cover,
CrystEngComm)
Volume 18
Issue 19

(2016)

Journal cover,CrystEngComm Volume 16 Issue 21 (2014)

(Journal cover,
CrystEngComm)
Volume 16
Issue 21

(2014)

 

Physica Status Solidi (a)) Volume 209 issue 6

(Journal cover,
Physica Status Solidi (a))
Volume 209
Issue 6

(2012)

 

Journal cover, Physica Status Solidi (a) Volume 208 Issue 1 (2011)

(Journal cover,
Physica Status Solidi (a))
Volume 208
Issue 1

(2011)

 

( Journal cover, IEEE Transactions on Nanotechnology) Volume 9 Issue 2  (2010)
( Journal cover,
IEEE Transactions on Nanotechnology)
Volume 9
Issue 2

(2010)

 

Wiley's Material Science online portal, Materials Views

(Materials Views, Wiley's Material Science)
"Nano Rings and Nano Pyramids"
(2010)

 


(Journal cover, Physica Status Solidi (a)) Volume 207 Issue 2  (2010)
(Journal cover,
Physica Status Solidi (a))
Volume 207
Issue 2

(2010)

 

(Journal cover, Applied Physics Letters) Volume 89 Issue 20  (2006)
(Journal cover,
Applied Physics Letters)
Volume 89
Issue 20

(2006)

 



(2006 MRS Fall Meeting Scene)
"Self-Assembly of InGaAs Quantum Dot Molecules (QDMs)"
(2006)

 

(Journal cover, Applied Physics Letters) Volume 88 Issue 23  (2006)

(Journal cover,
Applied Physics Letters)
Volume 88
Issue 23

(2006)

 

www.nanowerk.com

(NanoWerk, Spotlight)
"Quantum dot necklaces and other QD chains"
(April 12, 2006)

 

 


- PUBLICATIONS -

Journal Papers


* AUTHORS (in the order of authorship)
** TYPE: A: article, B: full book, CB: chapter of book, E: editor, & R: review, V: Video journal
***
IF: ISI® impact factor
*** Trend of Impact Factor of journals with interest (JCR IF 2015
)

 

TITLE: Ag Nanostructures on GaN (0001): Morphology Evolution controlled by the solid state dewetting of thin films and corresponding optical properties
AUTHORS: . Kunwar, M. Sui, Q. Zhang, P. Pandey, M. Y. Li and J. H. Lee
JOURNAL/BOOK TITLE:
Crystal growth & design
VOLUME: 16                                 FIRST PAGE: 6974
YEAR OF PUBLICATION:
2017                              KEY: A                      IF: 4.055


Abstract


 

Silver (Ag) nanostructures have demonstrated the feasibilities being utilized in various optoelectronic, catalytic, biomedical and sensor devices due to the excellent surface plasmon resonance characteristics. The geometrical structure, spacing and spatial arrangement of nanostructures are crucial for controlling the properties and device performance. Herein, we demonstrate the fabrication of various configurations of self-assembled Ag nanostructures on GaN (0001) by the systematic control of deposition thickness and annealing duration. The surface morphology evolution is thoroughly investigated and the corresponding influence on optical properties are probed. The evolution of Ag nanostructures in response to the thermal annealing is described based on the dewetting of thin films, Volmer-Weber growth model, coalescence growth and surface energy minimization mechanism. For the deposition amount variation between 1 and 100 nm, the Ag nanostructures show gradual morphological transitions such as: small NPs to enlarged NPs between 1 and 7 nm, elongated nanostructures to cluster networks between 10 and 30 nm and void evolution with layered nanostructures between 40 and 100 nm. In addition, the annealing duration effect has been studied between 0 and 3600 s, where the Ag nanostructures exhibit the evolution of network-like, elongated and isolated irregular shapes, ascribed to the Ostwald’s ripening along with the Ag sublimation. Furthermore, the corresponding Raman, photoluminescence (PL) and reflectance spectra reveal the morphology dependent behaviors and are discussed based on the phonon, emission band, scattering, absorption and surface plasmon effect.

 

Graphical Abstract



Ag Nanostructures on GaN (0001): Morphology Evolution controlled by the solid state dewetting of thin films and corresponding optical properties

Ag Nanostructures on GaN (0001): Morphology Evolution controlled by the solid state dewetting of thin films and corresponding optical properties

 

 

TITLE: Determination of growth regimes of Pd nanostructures on c-plane sapphire by the control of deposition amount at different annealing temperatures”
AUTHORS: S. Kunwar, M. Sui, P. Pandey, Q. Zhang, M. Y. Li, H. Bhandari and J. H. Lee
JOURNAL/BOOK TITLE:
Physical Chemistry Chemical Physics
VOLUME: 19                                 FIRST PAGE: 15084
YEAR OF PUBLICATION:
2017                              KEY: A                      IF: 4.123


Abstract


 

Metallic nanoparticles (NPs) with the tunable physical, optical and catalytic properties lead to a wide range of applications including various optoelectronics, sensors and fuel cells. In this paper, we demonstrate the evolution of various physical properties, configurations, size and density of palladium (Pd) nanostructures on sapphire (Al2O3) (0001) by the systematic control of deposition amount (DA) at distinct annealing temperatures. The transformation of deposited thin films into the various Pd NPs is achieved by the dewetting of thin film by means of surface diffusion, nucleation, Volmer-Weber growth and surface energy minimization mechanism. Depending on the evolution of size, density and configuration, five distinctive regimes of Pd nanostructures are demonstrated: (i) nucleation and evolution of small NPs between 1 and 3 nm (ii) medium NPs with the dominating vertical growth between 5 and 20 nm, (iii) laterally expanded large NPs between 30 and 40 nm, (iv) irregular coalesced Pd NPs between 50 and 80 nm, and finally (v) voids evolution between 100 and 200 nm. Initial film thickness and annealing temperature play major roles on the dewetting process and the resulting Pd nanostructures are notably distinguished. The fabricated Pd nanostructures has the influence on the lattice vibration modes of sapphire (0001) such as gradual decrement in the intensity and left shift of peak position with the increased surface coverage. In addition, the optical properties are studied by UV-VIS-NIR (300 – 1100 nm) reflectance spectra, which shows the reflectance, absorption and scattering over the wavelength and are closely related to the morphology evolution of Pd nanostructures.

 

Graphical Abstract



Determination of growth regimes of Pd nanostructures on c-plane sapphire by the control of deposition amount at different annealing temperatures

Determination of growth regimes of Pd nanostructures on c-plane sapphire by the control of deposition amount at different annealing temperatures

 

TITLE: Au-assisted Fabrication of Nano-holes on c-plane Sapphire via Thermal Treatment guided by Au Nanoparticles as Catalysts
AUTHORS: M. Sui, P. Pandey, M. Y. Li, Q. Zhang, S. Kunwar and J. H. Lee
JOURNAL/BOOK TITLE:
Applied Surface Science
VOLUME: 39
3                                 FIRST PAGE: 23
YEAR OF PUBLICATION:
2017                              KEY: A                      IF: 3.387


Abstract


 

Nanoscale patterning of sapphires is a challenging task due to the high mechanical strength, chemical stability as well as thermal durability. In this paper, we demonstrate a gold droplet assisted approach of nano-hole fabrication on c-plane sapphire via a thermal treatment. Uniformly distributed nano-holes are fabricated on the sapphire surface guided by dome shaped Au nanoparticles (NPs) as catalysts and the patterning process is discussed based on the disequilibrium of vapor, liquid, solid interface energies at the Au NP/sapphire interface induced by the Au evaporation at high temperature. Followed by the re-equilibration of interface energy, transport of alumina from the beneath of NPs to the sapphire surface can occur along the NP/sapphire interface resulting in the formation of nano-holes. The fabrication of nano-holes using Au NPs as catalysts is a flexible, economical and convenient approach and can find applications in various optoelectronics.

 

Graphical Abstract



 

Au-assisted Fabrication of Nano-holes on c-plane Sapphire via Thermal Treatment guided by Au Nanoparticles as Catalysts

Au-assisted Fabrication of Nano-holes on c-plane Sapphire via Thermal Treatment guided by Au Nanoparticles as Catalysts

 

 

TITLE: Morphological and Optical Evolution of Silver Nanoparticles on Sapphire (0001) along with the Concurrent Influence of Diffusion, Ostwald’s Ripening and Sublimation
AUTHORS: P. Pandey,
S. Kunwar, M. Sui, Q. Zhang, M. Y. Li and J. H. Lee
JOURNAL/BOOK TITLE:
IEEE Transactions on Nanotechnology
VOLUME: 16                                 FIRST PAGE: 321
YEAR OF PUBLICATION:
2017                              KEY: A                      IF: 2.485


Abstract


 

Ag nanoparticles (NPs) have found a number of applications in various fields such as optoelectronics, sensors and catalysts and the optical, physical and chemical properties of Ag NPs can be modified by the control of size, density and configuration as well as their spacing. Therefore, in this paper, we demonstrate the size, shape and spacing control of Ag NPs by the systematic control of annealing duration between 0 and 3600 s on sapphire (0001) (Al2O3). The Ag NPs show a sharp distinction in morphology along with the controlled duration at 20 and 14 nm thickness and the evolution trend is systematically discussed based on the concurrent influence of surface diffusion, Ostwald’s ripening and sublimation. With the relatively thicker film of 20 nm, the fabrication of irregular and round NPs is demonstrated along with the gradually reduced size up on the annealing at 750 oC for the duration between 0 and 900 s. Between 1800 and 3600 s, tiny grain-like particles result as a consequence of an extensive sublimation. Meanwhile, with the film thickness of 14 nm at 400 oC, densely packed small NPs are resulted between 0 and 3600 s due to the limited surface diffusion. At the same time, the optical characterizations such as Raman and reflectance spectroscopy show a distinctive trend of spectra, i.e. intensity, peak position and FWHM, based on the evolution of Ag NPs and are discussed in conjunction with the specific morphology and surface coverage of the Ag NPs.

 

Graphical Abstract



Morphological and Optical Evolution of Silver Nanoparticles on Sapphire (0001) along with the Concurrent Influence of Diffusion, Ostwald’s Ripening and Sublimation

Morphological and Optical Evolution of Silver Nanoparticles on Sapphire (0001) along with the Concurrent Influence of Diffusion, Ostwald’s Ripening and Sublimation

 

 

 

TITLE: Study on the Dimensional, Configurational and Optical Evolution of Palladium Nanostructures on c-plane Sapphire by the Control of Annealing Temperature and Duration
AUTHORS:
M. Sui, Q. Zhang, S. Kunwar, P. Pandey, M. Y. Li and J. H. Lee
JOURNAL/BOOK TITLE:
Applied Surface Science
VOLUME: 416                                 FIRST PAGE: 1
YEAR OF PUBLICATION:
2017                              KEY: A                      IF: 3.387


Abstract


 

Metallic nanostructures can find various applications such as in optoelectronic devices, nanostructure synthesis and catalytic applications and their applicability vary depending on their size, density and configuration dependent properties. In this paper, the dimensional and configurational evolution of self-assembled palladium (Pd) nanostructures is systematically studied on c-plane sapphire with the control of annealing temperature (AT) and annealing duration with the initial Pd layers of various thicknesses. Depending on the AT, two distinct growth regimes are observed based on the concurrent effect of surface diffusion, surface energy minimization and Pd sublimation: i.e. (i) agglomeration of Pd nano-clusters from voids (500 < AT ≤ 650 °C) and (ii) round nanoparticle (NP) fabrication (650 °C < AT ≤ 900 °C). At 950 °C, due to the sublimation of Pd atoms, substantial decrease in the NP dimension is witnessed and results in the ring patterns around the NPs. Additional investigation is performed at 950 °C to reveal the annealing duration effect on the NP evolution. Due to the dual effect of the Oswald ripening and atom sublimation, initially the dimension of NPs is grown and then gradually decays along with the duration, resulting in an inverted ‘V’ pattern evolution in diameter and height. Moreover, the evolution of optical properties such as absorption band and average reflectance are studied with the corresponding reflectance spectra as a function of wavelength over UV, visible and NIR region. The Raman spectra analysis depicts the variation of lattice vibration peak intensity and position based on the surface morphology of the Pd nanostructures.

 

Graphical Abstract



Study on the Dimensional, Configurational and Optical Evolution of Palladium Nanostructures on c-plane Sapphire by the Control of Annealing Temperature and Duration

Study on the Dimensional, Configurational and Optical Evolution of Palladium Nanostructures on c-plane Sapphire by the Control of Annealing Temperature and Duration

 

 

 

TITLE: Determination of growth regimes of Pt nanostructures on GaN (0001) based on the control of Pt thickness and annealing time: morphological evolution of Pt nanostructures from the nanoparticles, nanoclusters to porous network
AUTHORS:
P. Pandey, M. Sui, S. Kunwar, M. Y. Li, Q. Zhang and J. H. Lee
JOURNAL/BOOK TITLE:
Journal of Materials: Design and Applications
VOLUME:                                  FIRST PAGE:
YEAR OF PUBLICATION:
2017                              KEY: A                      IF: 1.625


Abstract


 

Pt nanostructures are applicable in various applications such as sensors, solar cells, light emitting devices (LEDs) and catalysis and only slight changes in their configuration, density and size can induce significant changes in their properties and thus the functionality in the related applications. In this paper, the systematical evolution of Pt nanostructures such as nanoparticles (NPs), nanoclusters and porous network on GaN (0001) is demonstrated by the systematic thermal annealing of Pt thin films based on the combinational effects such as thermal dewetting, Volmer-Weber growth model and coalescence growth. In particular, small dome shaped self-assembled Pt NPs with relatively smaller deposition amount (< 2 nm) and wiggly Pt nanoclusters between 3 and 5 nm are formed based on the Volmer-Weber growth model and the partial coalescence of Pt NPs respectively. Between 10 and 30 nm, the growth of Pt nanoclusters is observed and eventually with the increased Pt thickness range between 40 and 100 nm, nanoclusters gradually develop into the porous Pt network by connecting neighboring structures owing to the enhanced coalescence growth. Meanwhile, along with the annealing time variation between 0 and 3600 s, the rate of dewetting is increased and as a result the evolution of densely packed to separated nanoclusters are formed. In addition, the optical properties of corresponding Pt nanostructures demonstrate that the photoluminescence (PL) and Raman intensity are reduced along with the evolution of the surface coverage of Pt nanostructures whereas the average reflectance is significantly enhanced accordingly at the same time.

 

Graphical Abstract



Determination of growth regimes of Pt nanostructures on GaN (0001) based on the control of Pt thickness and annealing time: morphological evolution of Pt nanostructures from the nanoparticles, nanoclusters to porous network

Determination of growth regimes of Pt nanostructures on GaN (0001) based on the control of Pt thickness and annealing time: morphological evolution of Pt nanostructures from the nanoparticles, nanoclusters to porous network

 

 

 

TITLE: Effects of Annealing Temperature and Duration on the Morphological and Optical Evolution of Self-Assembled Pt Nanostructures on c-plane Sapphire
AUTHORS:
M. Sui, M. Y. Li, S. Kunwar, P. Pandey,Q. Zhang, and J. H. Lee
JOURNAL/BOOK TITLE:
PLOS ONE
VOLUME: 12                                 FIRST PAGE: e0177048
YEAR OF PUBLICATION:
2017                              KEY: A                      IF: 2.806


Abstract


 

Metallic nanostructures (NSs) have been widely adapted in various applications and their physical, chemical, optical and catalytic properties are strongly dependent on their surface morphologies. In this work, the morphological and optical evolution of self-assembled Pt nanostructures on c-plane sapphire (0001) is demonstrated by the control of annealing temperature and dwelling duration with the distinct thickness of Pt films. The formation of Pt NSs is led by the surface diffusion, agglomeration and surface and interface energy minimization of Pt thin films, which relies on the growth parameters such as system temperature, film thickness and annealing duration. The Pt layer of 10 nm shows the formation of overlaying NPs below 650 °C and isolated Pt nanoparticles above 700 °C based on the enhanced surface diffusion and Volmer-Weber growth model whereas larger wiggly nanostructures are formed with 20 nm thick Pt layers based on the coalescence growth model. The morphologies of Pt nanostructures demonstrate a sharp distinction depending on the growth parameters applied. By the control of dwelling duration, the gradual transition from dense Pt nanoparticles to networks-like and large clusters is observed as correlated to the Rayleigh instability and Ostwald ripening. The various Pt NSs show a significant distinction in the reflectance spectra depending on the morphology evolution: i.e. the enhancement in UV-visible and NIR regions and the related optical properties are discussed in conjunction with the Pt NSs morphology and the surface coverage.

 

Graphical Abstract



Effects of Annealing Temperature and Duration on the Morphological and Optical Evolution of Self-Assembled Pt Nanostructures on c-plane Sapphire

Effects of Annealing Temperature and Duration on the Morphological and Optical Evolution of Self-Assembled Pt Nanostructures on c-plane Sapphire

 

 

 

TITLE: Effect of Systematic Control of Pd Thickness and Annealing Temperature on the Fabrication and Evolution of Palladium Nanostructures on Si (111) via the Solid State Dewetting
AUTHORS:
S. Kunwar, P. Pandey, M. Sui, Q. Zhang, M. Y. Li and J. H. Lee
JOURNAL/BOOK TITLE:
Nanoscale Research Letters
VOLUME: 12                                  FIRST PAGE: 364
YEAR OF PUBLICATION:
2017                              KEY: A                      IF: 2. 833


Abstract


 

Si-based optoelectronic devices embedded with metallic nanoparticles (NPs) have demonstrated the NP shape, size, spacing and crystallinity dependent light absorption and emission induced by the localized surface plasmon resonance. In this work, we demonstrate various size and configuration of palladium (Pd) nanostructures on Si (111) by the systematic thermal annealing with the variation of Pd thickness and annealing temperature. The evolution of Pd nanostructures are systematically controlled by the dewetting of thin film by means of the surface diffusion in conjunction with the surface and interface energy minimization and Volmer-weber growth model. Depending on the control of deposition amount ranging between 0.5 and 100 nm at various annealing temperature, four distinctive regimes of Pd nanostructures are demonstrated: i) small pits and grain formation, ii) nucleation and growth of NPs, iii) lateral evolution of NPs and iv) merged nanostructures. In addition, by the control of annealing between 300 and 800 ºC, the Pd nanostructures show the evolution of small pits and grains, isolated NPs and finally Pd NP assisted nano-hole formation along with the Si decomposition and Pd-Si inter-diffusion. The Raman analysis showed the discrepancies on phonon modes of Si (111) such that the decreased peaks intensity with left shift after the fabrication of Pd nanostructures. Furthermore, the UV-VIS-NIR reflectance spectra revealed the existence of surface morphology dependent absorption, scattering and reflectance properties.

 

Graphical Abstract



Effect of Systematic Control of Pd Thickness and Annealing Temperature on the Fabrication and Evolution of Palladium Nanostructures on Si (111) via the Solid State Dewetting

Effect of Systematic Control of Pd Thickness and Annealing Temperature on the Fabrication and Evolution of Palladium Nanostructures on Si (111) via the Solid State Dewetting

 

 

 

TITLE: Nanoscale morphology and optical property evolution of Pt Nanostructures on GaN (0001) by the systematic control of Annealing Temperature and Duration with various Pt thickness
AUTHORS:
S. Kunwar, P. Pandey, M. Sui, Q. Zhang, M. Y. Li and J. H. Lee
JOURNAL/BOOK TITLE:
Materials Research Express
VOLUME:  4                                FIRST PAGE: 065019
YEAR OF PUBLICATION:
2017                              KEY: A                      IF: 1.068


Abstract


 

By the controlled fabrication of Pt nanostructures, various surface morphology dependent electronic, catalytic and optical properties can be exploited for the wide range of applications. In this paper, the evolution of Pt nanostructures on GaN (0001) by the solid-state dewetting of Pt thin films is investigated. Controlling the annealing temperature, time and film thickness allow to fabricate distinct size, density and configurations of Pt nanostructures. For 10 nm Pt thickness, tiny voids and Pt hillocks up to 550 °C, extensive void expansion and Pt nanostructure evolution between 600 and 750 °C and finally Pt nanostructures assisted nanoholes penetration on GaN surface above 800 °C are demonstrated. Furthermore, comparatively elongated Pt nanostructures and NHs are resulted with 20 nm Pt thickness and voids growth and connected Pt nanostructure are formed by annealing duration control. The transformation of Pt films to nanostructures is governed by the surface diffusion, Rayleigh instability, Volmer-Weber growth and energy minimization mechanism whereas NHs penetration is commenced by the decomposition of GaN, Pt-Ga alloying and nitrogen desorption at high temperature. In addition, the optical characteristic of Pt nanostructures on GaN (0001) by reflectance, photoluminescence (PL) and Raman spectroscopy demonstrate the surface morphology dependent spectral response.

 

Graphical Abstract



Nanoscale morphology and optical property evolution of Pt Nanostructures on GaN (0001) by the systematic control of Annealing Temperature and Duration with various Pt thickness

Nanoscale morphology and optical property evolution of Pt Nanostructures on GaN (0001) by the systematic control of Annealing Temperature and Duration with various Pt thickness

 

 

 

TITLE: Fabrication and determination of growth regimes of various Pd NPs based on the control of deposition amount and temperature on c-plane GaN
AUTHORS:
M. Sui, S. Kunwar, P. Pandey, Q. Zhang, M. Y. Li and J. H. Lee
JOURNAL/BOOK TITLE:
b
VOLUME:                                  FIRST PAGE:
YEAR OF PUBLICATION:
2017                              KEY: A                      IF: 1.673


Abstract


 

Palladium (Pd) nanostructures have been actively adapted for various applications and the properties and applicability are closely depending on their shape, size and density. In this paper, the evolution of self-assembled Pd nanostructures on hexagonal c-plane GaN is presented by the systematical control of Pd deposition amount (DA) at distinctive temperatures. Pd nanostructures of various configuration, size and density are demonstrated based on the solid-state dewetting of Pd thin films and a clear distinction in the growth regimes is observed. Three growth regimes are clearly observed depending on the variation of DA: i.e. (i) the agglomeration of Pd nanoparticles (NPs), (ii) the coalescence of wiggly Pd nanostructures and finally (iii) the growth of nano-voids and layer. Owing to the temperature dependent dewetting process, the growth regimes are markedly shifted, resulting in the distinctive Pd nanostructures within the identical DA range. The results are discussed in conjunction with the surface diffusion, Volmer-Weber and coalescence growth model, and surface/interface energy minimization mechanism. In addition, the evolution of optical properties, emission band and lattice properties are probed by reflectance, PL and Raman spectroscopy, which exhibits varying spectral intensity and peak positions according to the surface morphology of Pd nanostructures.

 

Graphical Abstract



Fabrication and determination of growth regimes of various Pd NPs based on the control of deposition amount and temperature on c-plane GaN

Fabrication and determination of growth regimes of various Pd NPs based on the control of deposition amount and temperature on c-plane GaN

 

 

 

TITLE: “Effect of Annealing Temperature on Morphological and Optical Transition of Silver Nanoparticles on c-Plane Sapphire”
AUTHORS: P. Pandey,
S. Kunwar, M. Sui, M. Y. Li, Q. Zhang,and J. H. Lee
JOURNAL/BOOK TITLE:
Journal of Nanoscience and Nanotechnology
VOLUME: 17                                FIRST PAGE:
YEAR OF PUBLICATION:
2017                              KEY: A                      IF: 1.483


Abstract


 

As a promising candidate for the improved performance, silver nanoparticles (Ag NPs) have been successfully adapted in various applications such as photovoltaics, light emitting diodes (LEDs), sensors and catalysis by taking the advantage of their controllable plasmonic properties. In this paper, the control on the morphologies and optical properties of Ag NPs on c-plane sapphire (0001) is demonstrated by the systematic control of annealing temperature (between 200 and 950 oC) with 20 and 6 nm thick Ag films through the solid state dewetting. With the relatively thicker film of 20 nm, various configuration and size of Ag NPs are fabricated such as irregular, round dome-shaped and tiny Ag NPs depending on the annealing temperature. In a shrill contrast, the 6 nm Ag set exhibits a sharp distinction with the formation of densely packed small NPs and ultra-highly dense tiny Ag NPs due to the higher dewetting rate. While, the surface diffusion assumes the main driving force in the evolution process of Ag NP morphologies up to 550 °C, the sublimation of Ag atoms has played a significant role on top on the surface diffusion between 600 and 950 °C. The reflectance spectra of Ag NPs exhibit the quadrupolar resonance and dipolar resonance peaks, and the evolution of peaks, shift and average reflectance were discussed based on the Ag NPs size and surface coverage. In particular, the dipolar resonance peak in the reflectance spectra red shifts from ~ 475 to ~ 570 nm due to the size increment of Ag NPs (38.31 to 74.68 nm). The wide surface coverage of Ag NPs exhibits the highest average reflectance (~ 27 %) and the lowest Raman intensity.

 

Graphical Abstract



Effect of Annealing Temperature on Morphological and Optical Transition of Silver Nanoparticles on c-Plane Sapphire

Effect of Annealing Temperature on Morphological and Optical Transition of Silver Nanoparticles on c-Plane Sapphire

 

 

 

TITLE: Various Silver Nanostructures on Sapphire Using Plasmon Self-Assembly and Dewetting of Thin Films
AUTHORS:
S. Kunwar, M. Sui, Q. Zhang, P. Pandey, M. Y. Li and J. H. Lee
JOURNAL/BOOK TITLE:
Nano-Micro Letters
VOLUME: 9                                 FIRST PAGE: 17
YEAR OF PUBLICATION:
2016                              KEY: A                      IF: 4.849


Abstract


 

Silver (Ag) nanostructures demonstrate outstanding optical, electrical, magnetic and catalytic properties and are being utilized in the range of application such as photonic, energy, sensors and biomedical devices. The target application and the performance can be inherently tuned by the control of configuration, shape and size of Ag nanostructures. In this work, we demonstrate the systematical fabrication of various configurations of Ag nanostructures on sapphire (0001) controlled by the Ag deposition thickness at various annealing environment. In particular, depending on the thickness of Ag thin film at 550 °C, the evolution of Ag particles (between 2 and 20 nm), irregular nanoclusters (between 30 and 60 nm) and nanocluster networks (between 80 and 200 nm) are demonstrated. The results are systematically analyzed and explained based on the solid-state dewetting, surface diffusion, Volmer-Weber growth model, coalescence and surface energy minimization mechanism. The growth behavior of Ag nanostructures is remarkably differentiated at higher annealing temperature (750 °C) due to the sublimation and temperature dependent characteristic of dewetting process. In addition, Raman and reflectance spectra analysis revealed the morphology dependence optical properties of Ag nanostructures.

 

Graphical Abstract



Various Silver Nanostructures on Sapphire Using Plasmon Self-Assembly and Dewetting of Thin Films

Various Silver Nanostructures on Sapphire Using Plasmon Self-Assembly and Dewetting of Thin Films

 

 

 

TITLE: Nanoparticles to Nanoholes: Fabrication of Porous GaN with Precisely Controlled Dimension via the Enhanced GaN Decomposition by Au nanoparticles
AUTHORS: P. Pandey, M. Sui, M. Y. Li, Q. Zhang, S. Kunwar,
J. Wu, Z. M. Wang, G. J. Salamo and J. H. Lee
JOURNAL/BOOK TITLE:
Crystal Growth & Design
VOLUME: 16                                 FIRST PAGE: 3334
YEAR OF PUBLICATION:
2016                              KEY: A                      IF: 4.891


Abstract


 

Porous GaN exhibits unique optoelectronic, chemical, and physical properties such as shift of band gap, increased surface area ratio, excellent chemical, mechanical, and thermal stability as well as efficient luminescence as compared to its bulk counterpart. Herein, we demonstrate a precise, efficient, and still cost-effective method of the fabrication of porous GaN through the enhanced GaN decomposition by using Au nanoparticles (NPs) as a catalyst, in which the size, density, and shape of the pores (nanoholes, NHs) can be precisely controlled. By the thermal annealing assisted with the Au NPs, the NHs are successfully fabricated, and the existence of Au NPs significantly accelerate the GaN decomposition at the interface between the NPs and GaN due to the Ga absorption by the Au NPs. We systematically study the formation mechanism of NHs assisted by the Au NPs by means of annealing temperature, duration, and Au deposition amount, and the results are systematically analyzed and discussed.

 

Graphical Abstract



Nanoparticles to Nanoholes: Fabrication of Porous GaN with Precisely Controlled Dimension via the Enhanced GaN Decomposition by Au nanoparticles

Nanoparticles to Nanoholes: Fabrication of Porous GaN with Precisely Controlled Dimension via the Enhanced GaN Decomposition by Au nanoparticles

 

 


TITLE: Journal Cover: Precise Control of Configuration, Size and Density of Self-assembled Au Nanostructures on 4H-SiC (0001) by Systematic Variation of Deposition Amount, Annealing Temperature and Duration
AUTHORS: M. Y. Li, M. Sui,P. Pandey, Q. Zhang, S. Kunwar, G. J. Salamo and J. H. Lee
JOURNAL/BOOK TITLE:
CrystEngComm
VOLUME: 18                                  FIRST PAGE: 3347
YEAR OF PUBLICATION:
2016                              KEY: A                      IF: 4.043
Journal Cover: Precise Control of Configuration, Size and Density of Self-assembled Au Nanostructures on 4H-SiC (0001) by Systematic Variation of Deposition Amount, Annealing Temperature and Duration
 

 

TITLE: Precise Control of Configuration, Size and Density of Self-assembled Au Nanostructures on 4H-SiC (0001) by Systematic Variation of Deposition Amount, Annealing Temperature and Duration
AUTHORS: M. Y. Li, M. Sui,P. Pandey, Q. Zhang, S. Kunwar, G. J. Salamo and J. H. Lee
JOURNAL/BOOK TITLE:
CrystEngComm
VOLUME: 18                                 FIRST PAGE: 3347
YEAR OF PUBLICATION:
2016                              KEY: A                      IF: 4.043


Abstract


 

The precise control over the configuration, size and density of Au nanoparticles (NPs) has offered an efficient route to enhance and optimize the performance and usability of various NP-based applications. In this study we successfully demonstrate the precise control of configuration, size and density of the self-assembled Au nanostructures on 4H-SiC (0001) via the systematic variation of deposition amount, annealing temperature and duration. Depending on the deposition amount at fixed annealing temperature and duration, the self-assembled Au NPs are successfully fabricated based on the Volmer-Weber growth model, and the NPs nucleate as round-dome shape and evolve into the hexagonal nano-crystals with the facet formation along with the increased deposition amounts. For the variation of annealing temperatures, the Au nanostructures radically develope into two distinct regimes: i.e. irregular Au nano-mounds (Regime I) between 400 and 700 °C based on the diffusion limited agglomeration (DLA) model and round-dome shaped droplets (DPs) (Regime II) between 750 and 900 °C. Depending on the dwelling time, the size and density evolution of round-dome shape Au DPs are dicusscussed based on the Ostwald-ripening theory.

 

Graphical Abstract



Precise Control of Configuration, Size and Density of Self-assembled Au Nanostructures on 4H-SiC (0001) by Systematic Variation of Deposition Amount, Annealing Temperature and Duration

Precise Control of Configuration, Size and Density of Self-assembled Au Nanostructures on 4H-SiC (0001) by Systematic Variation of Deposition Amount, Annealing Temperature and Duration

 

 

 

TITLE: Fabrication of Ag Nanostructures by the Systematic Control of Annealing temperature and duration on GaN (0001) via the Solid State Dewetting
AUTHORS: P. Pandey,
S. Kunwar, M. Sui, M. Y. Li, Q. Zhang and J. H. Lee
JOURNAL/BOOK TITLE:
Physica status solidi (a)
VOLUME: 214                                 FIRST PAGE: 1600702
YEAR OF PUBLICATION:
2016                              KEY: A                      IF: 1.775


Abstract


 

The gradual evolution of Ag nanostructures in terms of the configuration, size and density of via the solid state dewetting is demonstrated on GaN (0001) by the systematic control of annealing temperature and duration with various Ag film thickness. Upon the annealing between 150 and 700 oC with the 20 nm Ag film, the hillocks, voids, irregular and round dome shaped Ag nanoparticles (NPs) are fabricated based on various growth mechanisms: i.e. thermal diffusion, and sublimation as well as the surface energy minimization. On the other hand, along with the systematic control of annealing duration between 0 and 3600 s with 10 nm Ag film 700 oC, the Ag NPs show gradually decreased size and density based on the concurrent influence of the Ostwald’s ripening and sublimation of Ag atoms. The Raman, photoluminescence and reflectance spectroscopy of the resulting Ag NPs are characterized in accordance with the various morphology evolution of Ag nanostructures.

 

Graphical Abstract



 

Fabrication of Ag Nanostructures by the Systematic Control of Annealing temperature and duration on GaN (0001) via the Solid State Dewetting

Fabrication of Ag Nanostructures by the Systematic Control of Annealing temperature and duration on GaN (0001) via the Solid State Dewetting

 

 

 

TITLE: Metallic Nanodroplet Induced Coulomb Catalysis for Off-Resonant Plasmonic Enhancement of Photoemission in Semiconductors
AUTHORS: Arup Neogi, Karol Gryczynski, Antonio Llopis, Jie Lin, Kyle Main, Ryoko Shimada, Zhiming Wang, Jihoon Lee, Gregory Salamo, and Arkadii Krokhin
JOURNAL/BOOK TITLE:
ACS Omega
VOLUME: 1                                 FIRST PAGE: 19
YEAR OF PUBLICATION:
2016                              KEY: A  


Abstract


 

The enhancement of light from semiconductors due to surface plasmons coupled resonantly to its emission is limited because of dissipation in the metal and is also restricted by the dielectric characteristics and homogeneity of the metal−semiconductor interface. We report a new mechanism based on electrostatic interactions of carriers and their image charges in metals to generate more photons from optical sources at frequencies that are off-resonant to the localized plasmon frequency. Coulomb catalysis of carrier accumulation resulting from the inhomogeneity of metal nanodroplets on a semiconductor’s surface can result in an enhancement of light that is nondissipative and does not require resonant coupling of plasmons to the emission wavelength. The enhancement occurs because of an increase in the ratio of radiative to nonradiative recombination in the vicinity of metal nanoparticles. It is equally effective with any type of metal and enhances radiation at any frequency, a property that is of principal importance for the realization of widely tunable semiconductor emitters. This fundamental mechanism provides a new perspective for improving the efficiency of light emitters and controlling carrier concentration on the nanoscale. The structural characteristics of the hybrid metal−semiconductor emitters are studied using electron microscopy and atomic force microscopy. We demonstrate the electrostatic mechanism by studying steady-state and transient photoluminescence from two-dimensional semiconductors, such as GaAs/AlGAs quantum wells, and bulk semiconductors, such as ZnO thin films, emitting in the near-IR and UV wavelength regimes, respectively.

 

Graphical Abstract



Metallic Nanodroplet Induced Coulomb Catalysis for Off-Resonant Plasmonic Enhancement of Photoemission in Semiconductors

Metallic Nanodroplet Induced Coulomb Catalysis for Off-Resonant Plasmonic Enhancement of Photoemission in Semiconductors

Metallic Nanodroplet Induced Coulomb Catalysis for Off-Resonant Plasmonic Enhancement of Photoemission in Semiconductors

 

 

 

TITLE: Systematic Control of the Size, Density and Configuration of Pt Nanostructures on Sapphire (0001) by the Variation of Deposition Amount and Dwelling Time
AUTHORS: P. Pandey, M. Sui, Q. Zhang, M. Y. Li, S. Kunwar and J. H. Lee
JOURNAL/BOOK TITLE:
Applied Surface Science
VOLUME: 368                                 FIRST PAGE: 198
YEAR OF PUBLICATION:
2016                              KEY: A                      IF: 3.15


Abstract


 

Metal nanoparticles (NPs) with controllable size, density and configuration can significantly enhance the energy conversion efficiency, detection sensitivity and catalytic activity as witnessed in various optoelectronic, optical sensing and electro-catalytic devices due to their shape and size dependent properties. In this work, we systematically investigate the evolution of the size, density and configuration of Pt nanostructures on sapphire (0001). In particular, we have demonstrated four different configuration and evolution of Pt nanostructures with the systematic control of deposition amount (DA) based on the Volmer-Weber growth model in conjunction with the surface energy minimization mechanism, diffusion and coalescence. The various size and configuration of Pt nanostructures with respect to DA are (i) nucleation of mini-sized round shaped Pt NPs (1 ≤ DA ≤ 5 nm), (ii) growth of large sized Pt NPs (10 ≤ DA ≤ 15 nm), (iii) isolated irregular nanostructures (20 ≤ DA ≤ 30 nm) and (iv) coalesced Pt nanostructures (DA ≥ 40). On the other hand, with the increased dwelling time (DT), irregular Pt NPs are fabricated with the increased size and improved uniformity between 0 and 450 s of annealing. The growth of Pt NPs is saturated when the dwelling time reaches the critical value between 900 and 1800 s, which can be attributed to the Ostwald ripening.

 

Graphical Abstract



Systematic Control of the Size, Density and Configuration of Pt Nanostructures on Sapphire (0001) by the Variation of Deposition Amount and Dwelling Time

Systematic Control of the Size, Density and Configuration of Pt Nanostructures on Sapphire (0001) by the Variation of Deposition Amount and Dwelling Time

 

 

 

TITLE: Optical Properties of a Quantum Dot-Ring System Grown Using Droplet Epitaxy
AUTHORS: Gabriel Linares-García, Lilia Meza-Montes, Eric Stinaff, S. M. Alsolamy, M. E. Ware, Y. I. Mazur, Z. M. Wang, Jihoon Lee and G. J. Salamo
JOURNAL/BOOK TITLE:
Nanoscale Research Letters
VOLUME: 
11                                 FIRST PAGE: 309
YEAR OF PUBLICATION:
2016                              KEY: A                      IF: 2.779


Abstract


 

Electronic and optical properties of InAs/GaAs nanostructures grown by the droplet epitaxy method are studied. Carrier states were determined by k·p theory including effects of strain and In gradient concentration for a model geometry. Wavefunctions are highly localized in the dots. Coulomb and exchange interactions are studied and we found the system is in the strong confinement regime. Microphotoluminescence spectra and lifetimes were calculated and compared with measurements performed on a set of quantum rings in a single sample. Some features of spectra are in good agreement.

 

Graphical Abstract



 

Optical Properties of a Quantum Dot-Ring System Grown Using Droplet Epitaxy


Optical Properties of a Quantum Dot-Ring System Grown Using Droplet Epitaxy

 

 

 

TITLE: Evolution of Self-Assembled Ag Nanostructures on c-plane Sapphire by the Systematic Control of Annealing Temperature
AUTHORS: M. Sui, S. Kunwar, P. Pandey, M. Y. Li, Q. Zhang
and J. H. Lee
JOURNAL/BOOK TITLE:
Superlattices and Microstructures
VOLUME: 100                                 FIRST PAGE: 1128
YEAR OF PUBLICATION:
2016                              KEY: A                      IF: 2.123


Abstract


 

The morphological evolution of various Ag nanostructures on c-plane sapphire is systematically investigated through the solid-state-dewetting by the control of annealing temperature between 200 and 950 °C with the Ag films of 60 and 10 nm. Various configurations of Ag nanostructures including Ag voids, wiggly and round nanoparticles are fabricated with the 60 nm due to the annealing temperature dependent surface diffusion, surface energy minimization and Ag sublimation. As a sharp distinction, highly dense semi-spherical nanoparticles are fabricated with the 10 nm set throughout the temperature range due to a much higher dewetting degree induced by the enhanced surface diffusion with a much thinner film. The reflectance spectra shows a spectral shift along with the size variation, i.e. blue shift with the decreased size and vice versa. The reflectance and Raman spectra reveal a sharp distinction between the two sets along with the strong correlation to the nanostructure morphology.

 

Graphical Abstract



 

Evolution of Self-Assembled Ag Nanostructures on c-plane Sapphire by the Systematic Control of Annealing Temperature

Evolution of Self-Assembled Ag Nanostructures on c-plane Sapphire by the Systematic Control of Annealing Temperature

 

 

 

TITLE: Tuning the Configuration of Au Nanostructures: From Vermiform-like, Rod-like, Triangular, Hexagonal, to Polyhedral Nanostructures on c-plane GaN
Full Text Access: http://rdcu.be/j3CD
AUTHORS: M. Sui, P. Pandey, M. Y. Li, Q. Zhang, S. Kunwar
and J. H. Lee
JOURNAL/BOOK TITLE:
Journal of Material Science
VOLUME: 51                                  FIRST PAGE: 1 - 17
YEAR OF PUBLICATION:
2016                              KEY: A                      IF: 2.302


Abstract


 

The systematic control over the configuration, size and density of Au nanostructures can directly improve or optimize the physical, chemical and optoelectronic properties and thus the functionality in the related applications. In this work, we successfully demonstrate the systematic configurational transition of self-assembled Au nanostructures on c-plane GaN via the precise control of annealing temperature, deposition amount and annealing duration. Depending on the control of annealing temperature, self-assembled Au vermiform-like nanostructures are fabricated and evolve into the faceted Au nanorods and Au hexagons with the minimization of overall surface energy based on the Volmer-Weber growth model. With the deposition amount control, the volume-dependent transition of Au nanostructure configurations from triangles to hexagons and then to polyhedral is clearly observed and discussed based on the combinational effects of growth kinetics and surface free energy distribution. The configurational transition from irregular Au clusters to faceted nanostructures is witnessed along with the incremental variation of annealing duration based on the Ostwald-ripening.

 

Graphical Abstract



Tuning the Configuration of Au Nanostructures: From Vermiform-like, Rod-like, Triangular, Hexagonal, to Polyhedral Nanostructures on c-plane GaN

Tuning the Configuration of Au Nanostructures: From Vermiform-like, Rod-like, Triangular, Hexagonal, to Polyhedral Nanostructures on c-plane GaN

 

 

 

TITLE: Evolution of Morphological and Optical Properties of Self-assembled Ag Nanostructures on c-plane Sapphire (0001) by the precise control of Deposition Amount
AUTHORS:
S. Kunwar, , M. Y. Li, P. Pandey, M. Sui, Q. Zhang and J. H. Lee
JOURNAL/BOOK TITLE:
Materials Research Express
VOLUME: 3                                 FIRST PAGE: 125006
YEAR OF PUBLICATION:
2016                              KEY: A                      IF: 1.068


Abstract


 

Silver (Ag) nanoparticles (NPs) have been widely adapted in various optoelectronic and sensing applications due to the size, shape and density dependent tunable properties. In this work, the systematic control of the size, configuration and density of self-assembled Ag nanostructures on c-plane sapphire (0001) is demonstrated through the solid state dewetting process by the variation of deposition amount (DA) at two distinctive temperature of 400 and 650 °C. The corresponding morphological evolution of Ag nanostructures is systematically discussed based on the diffusion, Volmer-Weber and coalescence growth model. In specific, at the relatively lower temperature of 400 °C, the Ag nanostructures evolve in three distinctive regimes based on the DA control: i.e. the dome-shaped Ag NPs between 2 and 14 nm (regime I), the irregular nano-mounds (NMs) between 20 and 40 nm (regime II), and the coalescence of Ag NMs into a layer between 60 and 200 nm (regime III). Meanwhile, at the relatively higher temperature of 650 °C, due to growth regime shift induced by the enhanced surface diffusion based on the increased thermal energy, the connected Ag NMs are resulted even at higher DAs and evolve along with the gradually increased DAs. The evolution of optical properties such as average reflectivity, plasmonic absorption band and the reflectance maxima (peaks) very sensitively respond to the evolution of size, shape and spacing of Ag nanostructures and discussed based on the surface plasmon, reflection and scattering. Specifically, the dome-shaped configuration exhibits strong absorption in the NIR region and weak absorption in visible region while the elongated NMs show the enhanced absorption in visible region. Furthermore, the Raman spectra (A1g vibrational mode) of the Ag nanostructures demonstrate the strong correlation with the evolution of size, density and surface coverage of the nanostructures.

 

Graphical Abstract



Evolution of Morphological and Optical Properties of Self-assembled Ag Nanostructures on c-plane Sapphire (0001) by the precise control of Deposition Amount

Evolution of Morphological and Optical Properties of Self-assembled Ag Nanostructures on c-plane Sapphire (0001) by the precise control of Deposition Amount

 

 

 

TITLE: From the Au nano-clusters to the nanoparticles on 4H-SiC (0001)
AUTHORS: M. Y. Li, Q. Zhang,P. Pandey, M. Sui, E. S. Kim and J. H. Lee
JOURNAL/BOOK TITLE:
Scientific Reports
VOLUME: 5                                  FIRST PAGE: 13954
YEAR OF PUBLICATION:
2015                              KEY: A                      IF: 5.578


Abstract


 

The control over the configuration, size, and density of Au nanoparticles (NPs) has offered a promising route to control the spatial confinement of electrons and photons, as a result, Au NPs with a various configuration, size and density are witnessed in numerous applications. In this work, we investigate the evolution of self-assembled Au nanostructures on 4H-SiC (0001) by the systematic variation of annealing temperature (AT) with several deposition amount (DA). With the relatively high DAs (8 and 15 nm), depending on the AT variation, the surface morphology drastically evolve in two distinctive phases, i.e. (I) irregular nano-mounds and (II) hexagonal nano-crystals. The thermal energy activates adatoms to aggregate resulting in the formation of self-assembled irregular Au nano-mounds based on diffusion limited agglomeration at comparatively low annealing temperature, which is also accompanied with the formations of hillocks and granules due to the dewetting of Au films and surface reordering. At high temperature, hexagonal Au nano-crystals form with facets along {111} and {100} likely due to anisotropic distribution of surface energy induced by the increased volume of NPs. With the small DA (3 nm), only dome shaped Au NPs are fabricated along with the variation of AT from low to elevated temperature.

 

Graphical Abstract



From the Au nano-clusters to the nanoparticles on 4H-SiC (0001)

From the Au nano-clusters to the nanoparticles on 4H-SiC (0001)

 

 

 

TITLE: Systematic Study on the Self-assembled Hexagonal Au Voids, Nano-clusters and Nanoparticles on GaN (0001)
AUTHORS: P. Pandey, M. Sui, M. Y. Li, Q. Zhang, E. S. Kim and J. H. Lee
JOURNAL/BOOK TITLE:
PLOS ONE
VOLUME: 10(8)
                                  FIRST PAGE: e0134637
YEAR OF PUBLICATION:
2015                              KEY: A                      IF: 3.324


Abstract


 

Au nano-clusters and nanoparticles (NPs) have been widely utilized in various electronic, optoelectronic, and bio-medical applications due to their great potentials. The size, density and configuration of Au NPs play a vital role in the performance of these devices. In this paper, we present a systematic study on the self-assembled hexagonal Au voids, nano-clusters and NPs fabricated on GaN (0001) by the variation of annealing temperature and deposition amount. At relatively low annealing temperatures between 400 and 600 oC, the fabrication of hexagonal shaped Au voids and Au nano-clusters are observed and discussed based on the diffusion limited aggregation model. The size and density of voids and nano-clusters can systematically be controlled. The self-assembled Au NPs are fabricated at comparatively high temperatures from 650 to 800 oC based on the Volmer-Weber growth model and also the size and density can be tuned accordingly. The results are symmetrically analyzed and discussed in conjunction with the diffusion theory and thermodynamics by utilizing AFM and SEM images, EDS maps and spectra, FFT power spectra, cross-sectional line-profiles and size and density plots.

 

Graphical Abstract



Systematic Study on the Self-assembled Hexagonal Au Voids, Nano-clusters and Nanoparticles on GaN (0001)

Systematic Study on the Self-assembled Hexagonal Au Voids, Nano-clusters and Nanoparticles on GaN (0001)

 

 

 

TITLE: Systematic Control of Self-Assembled Au Nanoparticles and Nanostructures Through the Variation of Deposition Amount, Annealing Duration, and Temperature on Si (111)
AUTHORS: M. Y. Li, M. Sui,P. Pandey, Q. Zhang, E. S. Kim and J. H. Lee
JOURNAL/BOOK TITLE:
Nanoscale Research Letters
VOLUME:  
10                                FIRST PAGE: 494
YEAR OF PUBLICATION:
2015                              KEY: A                      IF: 2.779


Abstract


 

The size, density, and configurations of Au nanoparticles (NPs) can play important roles in controlling the electron mobility, light absorption, and localized surface plasmon resonance, and further in the Au NP-assisted nanostructure fabrications. In this study, we present a systematical investigation on the evolution of Au NPs and nanostructures on Si (111) by controlling the deposition amount (DA), annealing temperature (AT), and dwelling time (DT). Under an identical growth condition, the morphologies of Au NPs and nanostructures drastically evolve when the DA is only slightly varied, based on the Volmer-Weber and coalescence models: i.e. I: mini NPs, II: mid-sized round dome-shaped Au NPs, III: large Au NPs, and IV: coalesced nanostructures. With the AT control, three distinctive ranges are observed: i.e., NP nucleation, Au NPs maturation and melting. The gradual dimensional expansion of Au NPs is always compensated with the density reduction, which is explained with the thermodynamic theory. The DT effect is relatively minor on Au NPs, a sharp contrast to other metallic NPs, which is discussed based on the Ostwald-ripening.

 

Graphical Abstract



Systematic Control of Self-Assembled Au Nanoparticles and Nanostructures Through the Variation of Deposition Amount, Annealing Duration, and Temperature on Si (111)

Systematic Control of Self-Assembled Au Nanoparticles and Nanostructures Through the Variation of Deposition Amount, Annealing Duration, and Temperature on Si (111)

 

 

 

TITLE: Diamagnetic and paramagnetic shifts in self-assembled InAs lateral quantum dot molecules
AUTHORS: Xinran Zhou, Miquel Royo, Weiwen Liu, Jihoon H. Lee, Gregory. J. Salamo, Juan I. Climente, and Matthew F. Doty
JOURNAL/BOOK TITLE:
Physical Review B
VOLUME: 91                                 FIRST PAGE: 205427
YEAR OF PUBLICATION:
2015                              KEY: A                      IF: 3.664


Abstract


 

We uncover the underlying physics that explains the energy shifts of discrete states of individual InAs lateral quantum dot molecules (LQDMs) as a function of magnetic fields applied in the Faraday geometry. We observe that ground states of the LQDM exhibit a diamagnetic shift while excited states exhibit a paramagnetic shift. We explain the physical origin of the transition between these two behaviors by analyzing the molecular exciton states with effective mass calculations. We find that charge carriers in delocalized molecular states can become localized in single QDs with increasing magnetic field. We further show that the net effects of broken symmetry of the molecule and Coulomb correlation lead to the paramagnetic response.

 

Graphical Abstract



Diamagnetic and paramagnetic shifts in self-assembled InAs lateral quantum dot molecules

Diamagnetic and paramagnetic shifts in self-assembled InAs lateral quantum dot molecules

 

 

 

TITLE: Evolution of Self-Assembled Au NPs by controlling Annealing Temperature and Dwelling Time on Sapphire (0001)
AUTHORS: J. H. Lee, P. Pandey, M. Sui, M. Y. Li, Q. Zhang and S. Kunwar
JOURNAL/BOOK TITLE:
Nanoscale Research Letters
VOLUME:  10                                FIRST PAGE: 380
YEAR OF PUBLICATION: 2015                              KEY: A                      IF:
2.779


Abstract


 

Au nanoparticles (NPs) have been utilized in a wide range of device applications as well as catalysts for the fabrication of nanopores and nanowires, in which the performance of the associated devices and morphology of nanopores and nanowires are strongly dependent on the size, density and configuration of the Au NPs. In this paper, the evolution of self-assembled Au nanostructures and NPs on sapphire (0001) is systematically investigated with the variation of annealing temperature (AT) and dwelling time (DT). At the low temperature range between 300 and 600 oC, three distinct regimes of the Au nanostructure configuration are observed i.e. the vermiform-like Au piles, irregular Au nano-mounds and Au islands. Subsequently, being provided with relatively high thermal energy between 700 to 900 oC, the round dome shaped Au NPs are fabricated based on the Volmer-Weber growth model. With the increased AT, the size of the Au NPs is gradually increased due to more favorable surface diffusion while the density is gradually decreased as a compensation. On the other hand, with the increased DT, the size and density of Au NPs decreases due to the evaporation of Au at relatively high annealing temperature at 950 oC.

 

Graphical Abstract



Evolution of Self-Assembled Au NPs by controlling Annealing Temperature and Dwelling Time on Sapphire (0001)

Evolution of Self-Assembled Au NPs by controlling Annealing Temperature and Dwelling Time on Sapphire (0001)

 

 

 

TITLE: Shape transformation of self-assembled Au nanoparticles by the systematic control of deposition amount on Sapphire (0001)
AUTHORS: P. Pandey, M. Sui, M. Y. Li, Q. Zhang, E. S. Kim and J. H. Lee
JOURNAL/BOOK TITLE:
RSC Advances
VOLUME: 5                                 FIRST PAGE: 66212
YEAR OF PUBLICATION:
2015                              KEY: A                      IF: 3.840


Abstract


 

The shape and size dependent optical, physical and chemical properties of isotropic and anisotropic gold nanoparticles (Au NPs) have attracted significant research interests for the applications in various optoelectronic devices. In this paper, we systematically study the evolution of shape and size of self-assembled Au NPs by the variation of Au deposition amount on Sapphire (Al2O3) (0001). With the sufficient thermal energy (1000 oC) provided, dome shape Au NPs are fabricated on sapphire based on the Volmer-Weber growth model, due to the isotropic surface energy distribution. Furthermore, we observe the incremental variation of Au deposition amount is responsible for the transformation of isotropic to anisotropic Au nanoparticles (nanocrystals). An anisotropic nanoparticles reflect variant properties in their different crystalline surfaces and thus the utilization of anisotropic nanoparticles can lead to the comparatively high efficiency of related device applications. The addition of Au deposition amount leads to the facet formation on the lowest possible energy crystalline planes of NPs such that the orientation of top facet of Au NPs are (111) plane parallel to the (0001) plane of sapphire. However, due to many other higher index facet formation, the NPs look almost dome shaped at high amount of Au deposition. Overall, the shape transformation of NPs from dome, truncated hexagonal pyramid, elongated truncated hexagonal pyramid, truncated cone to multifaceted dome is observed along with the variation of Au deposition amount on Sapphire (Al2O3) (0001).

 

Graphical Abstract



Shape transformation of self-assembled Au nanoparticles by the systematic control of deposition amount on Sapphire (0001)

Shape transformation of self-assembled Au nanoparticles by the systematic control of deposition amount on Sapphire (0001)

 

 

 

TITLE: Configuration, Dimension and Density Control of 3-D Gold Nanostructures on various Type-B GaAs surfaces by the Systematic Variation of Annealing Temperature, Annealing Duration and Deposition Amount
AUTHORS: D Lee, M. Sui, M. Y. Li, P. Pandey, Q. Zhang,
E. S. Kim and J. H. Lee
JOURNAL/BOOK TITLE:
3D Research
VOLUME:  
6                                FIRST PAGE: 28(1) - 28(14)
YEAR OF PUBLICATION:
2015                              KEY: A


Abstract


 

Metallic nanoparticles have received extensive research attention due to their potential to be utilized in catalytic, electronic and optical applications. Tunable feature of quantum effect related to the configuration, dimension as well as the density of nanoparticles makes them appropriate building blocks for their applications at the nano-scale. In this paper, we systematically investigate the fabrication of self-assembled Au nanoparticles on high–index type-B GaAs (n11), where n is 9, 8, 4, and 2. By means of varying annealing temperature, Au deposition amount and annealing duration, the evolution of Au nanoparticles in terms of the average height, lateral diameter and average density is systematically studied. We observe that the variation of annealing temperature leads to an abrupt configuration evolution from the wiggly Au nanostructures to the round-dome shaped nanoparticles due to the limited and/or enhanced surface diffusion at various temperatures. Meanwhile, the variation of deposition amount leads to a wide range of dimensions of Au nanoparticles as a result of the size increase and the corresponding density decrease. Furthermore, based on the annealing duration control, the size of Au nanoparticles tends to be gradually increased owing to the Ostwald-ripening. Meanwhile, the effect of surface index on the size and density is also witnessed. The results are systematically analyzed by using the atomic force microscope images, energy-dispersive X-ray spectroscopy spectra and maps, Fourier filter transforms power spectra, cross-sectional line-profiles and size and density plots.

 

Graphical Abstract



Configuration, Dimension and Density Control of 3-D Gold Nanostructures on various Type-B GaAs surfaces by the Systematic Variation of Annealing Temperature, Annealing Duration and Deposition Amount

Configuration, Dimension and Density Control of 3-D Gold Nanostructures on various Type-B GaAs surfaces by the Systematic Variation of Annealing Temperature, Annealing Duration and Deposition Amount

 

 

 

TITLE: Observation of Shape, Configuration, and Density of Au Nanoparticles on Various GaAs Surfaces via Deposition Amount, Annealing Temperature, and Dwelling Time
AUTHORS: D. Lee, M. Y. Li,
M. Sui, Q. Zhang, P. Pandey, E. S. Kim and J. H. Lee
JOURNAL/BOOK TITLE:
Nanoscale Research Letters
VOLUME:  
10                                FIRST PAGE: 240
YEAR OF PUBLICATION:
2015                              KEY: A                      IF:2.779


Abstract


 

Metallic nanoparticles have been widely witnessed in many applications: serving as the catalysts for various nanowire systems, as the active mediums of various device applications, and also for the nanoscale templates for hybrid quantum structures. In the performance of devices and configurations of the resulting nanostructures, the size and density of nanoparticles play critical roles. In this paper, the control of self-assembled Au droplets on GaAs (100), (110), and (111) is systematically investigated through the variation of deposition amount (DA), annealing temperature (AT), and dwelling time (DT). Based on the
Volmer–Weber growth model, the formation of Au droplets and dramatic evolution of Au nanostructures on various GaAs surfaces is observed from the Au clusters to the round-dome shapes with the AT variation between 250 and 550 °C. With the systematic DA control, a radical size and density evolution of Au droplets shows the size expansion of over 400 % in average height and 800 % in average lateral diameter, while the density shows over two orders of decrease. With the DT variation, the self-assembled Au droplets tend to grow larger due to the Ostwald ripening while a clear distinction among the surface indexes is observed.

 

Graphical Abstract



Observation of Shape, Configuration, and Density of Au Nanoparticles on Various GaAs Surfaces via Deposition Amount, Annealing Temperature, and Dwelling Time

Observation of Shape, Configuration, and Density of Au Nanoparticles on Various GaAs Surfaces via Deposition Amount, Annealing Temperature, and Dwelling Time

 

 

 
Copyright © Advanced Quantum-Nano Materials & Optoelectronics Laboratory. All rights reserved.